The present invention relates to a device for mechanically cleaning wire rod to be used in processes for the production of drawn metal wires.
xe2x80x9cWire rodxe2x80x9d is used to refer to a semi-finished metallurgical product which is long and has a round cross-section and which, by means of gradual reduction of its cross-section during the technological process known as drawing, is reduced into the form of a wire.
The wire rod is hot-manufactured and is normally covered with oxides, hydroxides and calamine which must be removed before starting the actual drawing operation. If this operation were not carried out, poor quality wires would be obtained, the dies in which drawing is performed would be subject to rapid wear and there would be a significant restriction in the speed of the entire production process. The known operating methods for preparing wire rod for drawing are based on the use of chemical processes or, alternatively, mechanical processes. Although the use of chemical processes is able to ensure a higher level of cleaning quality, it nevertheless results in increased management and plant running costs and, in particular, creates serious problems with regard to environmental pollution. The use of mechanical processes is nowadays preferable because, although it results in an inferior cleaning quality of the wire rod, it involves lower plant management and operating costs and is less damaging for the environment.
Devices for mechanically cleaning wire rod, involving the use of a press comprising gripping jaws which support steel wool or another type of abrasive material wound around the wire rod, pressing it at the same time against the wire rod, are known and form the subject of previous patents in the name of the same Applicant. As the wire rod advances between the jaws, the steel wool removes the particles of oxide which cover the metal, but is not drawn along by the wire rod because the jaws retain it constantly, compensating for any wear with a gradual reduction in the space available therefor.
It is also useful, during mechanical cleaning, to prepare the surface of the wire rod with removal of metal particles using steel wool, in order to favour the subsequent operation consisting in fixing of a powdery lubricant. It is useful, however, to be able to modify, as required, the propensity of the wire rod to retain the lubricant depending on variable parameters, such as the chemical composition of the wire rod, the conditions for supplying of the semi-finished product, the type of lubricant and the drawing speed; and in particular it may be advantageous to maximize this propensity by increasing the length of the incisions formed on the surface of the wire rod, without modifying the longitudinal extension.
These further objects have been achieved with a device in which the jaws which grip the steel wool against the wire rod are able to rotate, at a variable speed, around the wire rod, forming helical grooves in the surface of the latter. Given a constant speed of feeding of the wire rod, the grooves have a spacing which is inversely proportional to the speed of rotation of the jaws, adjustment of which may therefore allow effective control over the propensity of the wire rod to retain the lubricant. The use of this device has, however, revealed certain drawbacks which are difficult to eliminate: in particular, the monolithic structure of the jaws results in an irregular contact surface with the steel wool which is formed, on the other hand, of loose material of a non-uniform nature, resulting in efficient pressure only in certain zones along the axis of the device. The need for mechanical balancing results in the use of jaw synchronization means located halfway along the axial extension of the jaws, with partial obstruction of the zone where the steel wool exerts its abrasive action on the wire rod. Finally, rotation of the jaws may result in twisting of the wire rod, resulting in compromises with negative effects in terms of operation of the device: for example, a necessary reduction in the speed of rotation or smaller dimensions of the device in the axial direction, i.e. parallel to the direction of feeding of the wire rod.
The object of the present invention is therefore to eliminate the drawbacks mentioned above. In accordance with the invention, this object is achieved by means of a device for mechanically cleaning wire rod, of the type indicated in the preamble of claim 1, in which the jaws which grip the steel wool, or other abrasive material, against the wire rod are supported by operating members consisting of adjacent and independent pairs of floating plates.
The main advantage obtained by means of the present invention consists in the fact that a uniform distribution, in the axial direction, of the pressure exerted by the jaws on the abrasive material is achieved and therefore the efficiency of the device is optimized. Moreover, the mechanical balancing, which is independent for each pair of plates, is advantageously achieved without obstructing the zone where the steel wool rubs against the wire rod; the structure of the plates may be lightened since their mutual independence replaces the considerable inertia of the monolithic device; as a result of the modularity of the jaws formed in this way, it is also possible to provide devices with dimensions satisfying the most widely varying requirements, keeping to a minimum the warehouse supplies, formed by plates which are all identical to each other. Finally, an important advantage consists in the fact that, for the same dimensions compared to the previously known device, the jaws may be formed by two sets of pairs of rotating plates which rotate in opposite directions to each other: in this way, twisting of the wire rod is compensated for and the surface of the latter has, etched on it, a double helix which will ensure a better propensity for retaining the lubricant and therefore an improved cleaning quality.